In the technological field of scanning antennas, increasing a scan angle is a very practical issue in order to improve the efficiency of a system. The scan angle of an antenna array of the related art is usually restricted to ±45 degrees without a considerable gain loss. However, special facilities are required for realization of the scan angle enhanced up to 70 degrees, especially for mobile devices, because optimal traffic varies within wide limits.
A conformal antenna array (cylindrical), Luneburg lens antennas, switchable axisymmetric antennas are applied to increase the scan angle. These types of antennas allow acquisition of a scan angle of ±90 and more. However, there are some drawbacks inherent for these antenna types.                1. The presence of an intricate switch inserting an additional loss.        2. Large spatial sizes.        3. Small efficiency of an antenna's aperture in a case of switched antennas.        
The antenna arrays of the related art are suitable for obtaining extended beam scanning by special structures installed in front of the arrays. These structures cause the additional front wave deflection. However, these structures are used usually for large arrays having wide sides.
Therefore, all of the afore-mentioned technologies are not suitable for designing very compact antenna devices.
There are some known solutions directed to creating a very compact phase antenna array that provides beam scanning over a possible wide range.
FIG. 7 illustrates an end-fire linear array antenna according to the related art.
Referring to FIG. 7, for example, U.S. Pat. No. 6,496,155 (End-fire antenna or array on surface with tunable impedance) discloses an antenna being an end-fire linear array. Elements of the array are located on the surface of a printed circuit board (PCB). Azimuth scanning is realized by phase relations between elements. A shortcoming with this array is a restricted scan angle (less than 40 degrees) due to lack of sufficiently wide beam of an elementary radiator.
FIG. 8 illustrates a planar one-dimension scanning lens antenna according to the related art.
Referring to FIG. 8, for example, a non-patent document “Beamforming Lens Antenna on a high resistivity silicon wafer for 60 GHz WPAN” (IEEE Transaction of Antennas and Propagation vol. 58, No 3, March 2010) discloses a planar one-dimension scanning lens antenna. The antenna is produced by PCB technology. Shortcomings with the antenna are a restricted scan angle (±40 degrees) and the need for a complicated switch for a beam steering operation.
FIG. 9 illustrates an antenna array including an active radiating element and one or more parasitic elements according to the related art.
Referring to FIG. 9, for example, U.S. Pat. No. 6,987,493 (Electrically steerable passive array antenna) discloses an antenna array including an active radiating element and one or more parasitic elements. Each parasitic antenna element is located on a circle around the radiating antenna element. The impedance of a passive element is changed by a tunable capacitor connected to each parasitic element. Due to an impedance variation, the phase of a reradiated wave is changed and as a result, the direction of a main beam is replaced. This antenna has a planar structure and provides circular one-plane scanning. Shortcomings with this antenna structure are a small front/back ratio, low directivity, one active channel only, and the need for active tunable elements and a DC controller.
FIG. 10 illustrates an antenna structure including two principal parts, a planar antenna array and a buckyball-shaped lens structure covering the antenna array according to the related art.
Referring to FIG. 10, for example, U.S. Pat. No. 8,493,281 (Lens for scanning angle enhancement of phased array antennas) considered as a prototype for the present disclosure discloses an antenna structure including two principal parts, a planar antenna array and a buckyball-shaped lens structure covering the antenna array. A design of the lens is created for a negative index metamaterial lens. The planar antenna array is employed for high directional beam forming and restricted beam scanning. The buckyball-shaped lens is capable of bending a beam generated by a phased array antenna at about 90 degrees. This solution also has shortcomings, the antenna array has very large spatial sizes. The spherical form of a declining lens does not allow application of this solution for integrating with portable devices, such as hand-held phones and tablet person computers (PCs).
Further, the previously known antennas that provide beam scanning have such drawbacks as high complexity in production and assembly, the presence of complicated switching and feeding circuits, and partial use of radiating elements.
Therefore, a need exists for a planar linear phase array antenna with enhanced beam scanning.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.